Leopard and zebra danios are actualy essentialy the same species so they behave pretty much the same.
I love zebra danios myself but be forwarned that they'll only shoal when scared or excited or when they are in a big tank with big fish and lots of ornaments or plants to bloack their line of sight a bit. Zebras and leopards and also most others of the more common danio types will school together. Just mixing the various color morphs and varieties of zebra danios can produce a remarkably varied display for such a common little fish.
White clouds doschool but realy white clouds are only borderline tropical and do better in slightly lower temps so I preffer to keep them with fish like bronze cories, danios, rubbernose plecs or other minnows that all enjoy a slightly lower temp.
IME, different cories will school together if there are only a few of their own species or if they are alone. However, if there are a number of each species, the schools will rarely mix. I generaly preffer to keep cories in groups of at least 4 of their own species. If you want to mix them, keep at least 2 of each species but at least 4 cories in total.
The best schooling fish are rasboras though - I know you said you didn't like them but I would think you have a harlequin in mind. If it's the red color you don't like, there are a few color morphs that are darker or have a slightly different pattern that you might preffer. If not, there are plenty of other rasboras to choose from! The The eye-spot rasbora (2.5"), spotted or pygmy rasbora (one of my favourites and only 1"), the red-line or red-striped or glowlight rasbora (2") and fire rasboras (1.5"). There are plenty of different kinds. However, if you think tetras are 'dumb', you'll probably think the same of most rasboras. Still, they are the very best schoolers and I find spotted rasboras in particular are very cute and have a lot of character for thei small size. BTW, there are many others such as the clown rasbora and scissortails which are lovely fish but get to 3" - I assumed that if tiger barbs were too large, so would these. However, rasboras need not be in groups of 7 to limmit aggression so a smaller group of these larger fish might work for you.
If you like barbs though, there are so many to choose from besides cherries that have a good, non-nippy temperament and the small size. Consider golden dwarf barbs which are great schoolers and only about 1.25", checker barbs at 2" and roloff's barb (lovely looking) that also grows to 2" but is a little more nippy IME. There are plenty of slightly larger ones too and the tropedo is an amazing fish if you are up to it.